The control of messenger RNA metabolism will be studied in human lymphocytes from the point at which mRNA precursors in the nucleus can be distinguished from bulk hnRNA, to the destruction of mature mRNA molecules in the cytoplasm. In vivo, the steps involved include control of transcription of hnRNA, selection of molecules for subsequent polyadenylation, transport of designated poly(A) positive as well as poly(A) negative components to the cytoplasm and the relationship between protein synthesis and the survival of particular mRNAs. Experiments to devise methods for inhibiting or activating these processes in order to manipulate cell growth are anticipated. The studies will encompass normal, resting and growing cells as well as cultured lines of lymphoid origin.